Endplate-preserving spinal implant with an integration plate having a roughened surface topography

ABSTRACT

An interbody spinal implant including a body having a top surface, a bottom surface, opposing lateral sides, opposing anterior and posterior portions, a substantially hollow center, and single vertical aperture, as well as an integration plate having a roughened surface topography on its top surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/151,198, filed on May 5, 2008, and pending, which is acontinuation-in-part of U.S. patent application Ser. No. 11/123,359,filed on May 6, 2005, and issued as U.S. Pat. No. 7,662,186. Thecontents of both prior applications are incorporated by reference inthis document, in their entirety and for all purposes.

FIELD OF THE INVENTION

The invention relates generally to interbody spinal implants and methodsof using such implants and, more particularly, to an implant includingan integration plate affixed to the implant body and having a roughenedsurface topography.

BACKGROUND OF THE INVENTION

In the simplest terms, the spine is a column made of vertebrae anddiscs. The vertebrae provide the support and structure of the spinewhile the spinal discs, located between the vertebrae, act as cushionsor “shock absorbers.” These discs also contribute to the flexibility andmotion of the spinal column. Over time, the discs may become diseased orinfected, may develop deformities such as tears or cracks, or may simplylose structural integrity (e.g., the discs may bulge or flatten).Impaired discs can affect the anatomical functions of the vertebrae, dueto the resultant lack of proper biomechanical support, and are oftenassociated with chronic back pain.

Several surgical techniques have been developed to address spinaldefects, such as disc degeneration and deformity. Spinal fusion hasbecome a recognized surgical procedure for mitigating back pain byrestoring biomechanical and anatomical integrity to the spine. Spinalfusion techniques involve the removal, or partial removal, of at leastone intervertebral disc and preparation of the disc space for receivingan implant by shaping the exposed vertebral endplates. An implant isthen inserted between the opposing endplates.

Several interbody implant systems have been introduced to facilitateinterbody fusion. Traditional threaded implants involve at least twocylindrical bodies, each typically packed with bone graft material,surgically placed on opposite sides of the mid-sagittal plane throughpre-tapped holes within the intervertebral disc space. This location isnot the preferable seating position for an implant system, however,because only a relatively small portion of the vertebral endplate iscontacted by these cylindrical implants. Accordingly, these implantbodies will likely contact the softer cancellous bone rather than thestronger cortical bone, or apophyseal rim, of the vertebral endplate.The seating of these threaded cylindrical implants may also compromisebiomechanical integrity by reducing the area in which to distributemechanical forces, thus increasing the apparent stress experienced byboth the implant and vertebrae. Still further, a substantial risk ofimplant subsidence (defined as sinking or settling) into the softercancellous bone of the vertebral body may arise from such improperseating.

In contrast, open ring-shaped cage implant systems are generally shapedto mimic the anatomical contour of the vertebral body. Traditionalring-shaped cages are generally comprised of allograft bone material,however, harvested from the human femur. Such allograft bone materialrestricts the usable size and shape of the resultant implant. Forexample, many of these femoral ring-shaped cages generally have amedial-lateral width of less than 25 mm. Therefore, these cages may notbe of a sufficient size to contact the strong cortical bone, orapophyseal rim, of the vertebral endplate. These size-limited implantsystems may also poorly accommodate related instrumentation such asdrivers, reamers, distractors, and the like. For example, these implantsystems may lack sufficient structural integrity to withstand repeatedimpact and may fracture during implantation. Still further, othertraditional non-allograft ring-shaped cage systems may be size-limiteddue to varied and complex supplemental implant instrumentation which mayobstruct the disc space while requiring greater exposure of theoperating space. These supplemental implant instrumentation systems alsogenerally increase the instrument load upon the surgeon.

The surgical procedure corresponding to an implant system shouldpreserve as much vertebral endplate bone surface as possible byminimizing the amount of bone removed. This vertebral endplate bonesurface, or subchondral bone, is generally much stronger than theunderlying cancellous bone. Preservation of the endplate bone stockensures biomechanical integrity of the endplates and minimizes the riskof implant subsidence. Thus, proper interbody implant design shouldprovide for optimal seating of the implant while utilizing the maximumamount of available supporting vertebral bone stock.

Nevertheless, traditional implantation practices often do not preservecritical bone structures such as vertebral endplates during the surgicalprocedure. In some cases, the implant devices themselves necessitateremoval of bone and were not designed or implanted with the intent topreserve critical bone structures during or after implantation.

In summary, at least ten, separate challenges can be identified asinherent in traditional anterior spinal fusion devices. Such challengesinclude: (1) end-plate preparation; (2) implant difficulty; (3)materials of construction; (4) implant expulsion; (5) implantsubsidence; (6) insufficient room for bone graft; (7) stress shielding;(8) lack of implant incorporation with vertebral bone; (9) limitationson radiographic visualization; and (10) cost of manufacture andinventory.

SUMMARY OF THE INVENTION

The invention is directed to interbody spinal implants and to methods ofusing such implants. The implants can be inserted, using methods of theinvention, from a variety of vantages, including anterior,antero-lateral, and lateral implantation. The spinal implant ispreferably adapted to be inserted into a prepared disc space via aprocedure which does not destroy the vertebral end-plates, or contactsthe vertebral end-plates only peripherally, allowing the intactvertebral end-plates to deflect like a diaphragm under axial compressiveloads generated due to physiologic activities and pressurize the bonegraft material disposed inside the spinal implant.

An implant preferably comprises a body and at least one integrationplate, which are joined together. The body preferably comprises a topsurface, a bottom surface, opposing lateral sides, opposing anterior andposterior portions, a substantially hollow center, and a single verticalaperture extending from the top surface to the bottom surface. Thevertical aperture has a size and shape for maximizing the surface areaof the top surface and the bottom surface available proximate theanterior and posterior portions while maximizing both radiographicvisualization and access to the substantially hollow center, defines atransverse rim with a varying width or thickness, and has a maximumwidth at its center between the opposing lateral sides. The anteriorportion of the body or the posterior portion of the body may comprise anopening for engaging a delivery device, facilitating delivery of bonegraft material to the substantially hollow center, enhancing visibilityof the implant, or providing access to bone graft material.

At least a portion of the top surface of the body is recessed andcomprises a plurality of holes in the recessed portion. In someembodiments, at least a portion of the bottom surface of the body isrecessed and comprises a plurality of holes in the recessed portion. Therecessed portion of the top surface and/or the recessed portion of thebottom surface are preferably recessed to a depth corresponding to thethickness of the integration plate.

The integration plate comprises a top surface, a bottom surface,opposing lateral sides, opposing anterior and posterior portions, and asingle vertical aperture extending from the top surface to the bottomsurface. Preferably, the vertical aperture aligns with the singlevertical aperture of the body, defines a transverse rim with a varyingwidth or thickness, and has a maximum width at its center. The topsurface of the integration plate comprises a roughened surfacetopography adapted to grip bone and inhibit migration of the implant.The bottom surface of the integration plate comprises a plurality ofposts positioned to align with the plurality of holes and affix theintegration plate to the body. The implant may comprise an integrationplate on the top surface and the bottom surface of the body.

The substantially hollow portion of the body may contain a bone graftmaterial adapted to facilitate the formation of a solid fusion columnwithin the spine. The bone graft material may be cancellous autograftbone, allograft bone, demineralized bone matrix (DBM), porous syntheticbone graft substitute, bone morphogenic protein (BMP), or a combinationthereof. The body may comprise a wall closing at least one of theopposing anterior and posterior portions of the body for containing thebone graft material.

The implant body and/or the integration plate may be fabricated from ametal. A preferred metal is titanium. The implant body may be fabricatedfrom a non-metallic material, non-limiting examples of which includepolyetherether-ketone, hedrocel, ultra-high molecular weightpolyethylene, and combinations thereof. The implant body may befabricated from both a metal and a non-metallic material, including acomposite thereof. For example, a composite may be formed, in part, oftitanium and, in part, of polyetherether-ketone, hedrocel, ultra-highmolecular weight polyethylene, or combinations thereof.

The body and the integration plate are preferably compatibly shaped,such that the implant with the body and integration plate joinedtogether may have a generally oval shape, a generally rectangular shape,a generally curved shape, or any other shape described or exemplified inthis specification. Thus, for example, the body and the integrationplate may be generally oval-shaped in transverse cross-section. The bodyand the integration plate may be generally rectangular-shaped intransverse cross-section. The body and the integration plate may begenerally curved-shaped in transverse cross-section.

The implant may comprise a lordotic angle adapted to facilitatealignment of the spine. At least one of the anterior and posteriorportions of the integration plate may comprise an anti-expulsion edge toresist pullout of the implant from the spine of a patient into which theimplant has been implanted.

The invention also features systems that include such interbody spinalimplants. The systems may comprise an implant and a distractor. Thesystems may further comprise a rasp. The systems may further comprise animplant holder capable of engaging an opening on the anterior portion ofthe spinal implant. The systems may further comprise a bone graftmaterial, non-limiting examples of which include cancellous autograftbone, allograft bone, demineralized bone matrix (DBM), porous syntheticbone graft substitute, bone morphogenic protein (BMP), or a combinationthereof.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawing are the following figures:

FIG. 1A shows a perspective view of an embodiment of the interbodyspinal implant having a generally oval shape and roughened surfacetopography on the top surface;

FIG. 1B shows a top view of the first embodiment of the interbody spinalimplant illustrated in FIG. 1A;

FIG. 2 shows a perspective view from the front of another embodiment ofthe interbody spinal implant according to the invention;

FIG. 3 shows a perspective view from the rear of the embodiment of theinterbody spinal implant illustrated in FIG. 2;

FIG. 4 shows a perspective view from the front of yet another embodimentof the interbody spinal implant according to the invention;

FIG. 5 shows a perspective view from the rear of the embodiment of theinterbody spinal implant illustrated in FIG. 4 highlighting analternative transverse aperture;

FIG. 6 shows a perspective view of another embodiment of the interbodyspinal implant having a generally oval shape and being especially welladapted for use in a cervical spine surgical procedure;

FIG. 7 shows a perspective view of an implant having a generally boxshape;

FIG. 8A shows an exploded view of a generally oval-shaped implant withan integration plate;

FIG. 8B shows an exploded view of a generally oval-shaped implant withintegration fixation and an integration plate;

FIG. 9 shows an exploded view of a curved implant with an integrationplate;

FIG. 10 shows an exploded view of a posterior implant with anintegration plate;

FIG. 11 shows an exploded view of a lateral lumbar implant with anintegration plate;

FIG. 12 shows an exploded view of a generally oval-shaped anteriorcervical implant with an integration plate;

FIG. 13A shows a cut-away view of an integration plate;

FIG. 13B shows a close-up of the cut-away portion illustrated in FIG.13A with the post of the integration plate fit within a hole in theimplant top surface;

FIG. 14A shows an exploded view of a pin connection suitable formounting an integration plate onto an implant;

FIG. 14B shows the pin connection illustrated in FIG. 14A with thecomponents assembled;

FIG. 14C shows a cut-away view of the pin connection illustrated inFIGS. 14A and 14B;

FIG. 14D shows an exploded view of a molded connection suitable formounting an integration plate onto an implant;

FIG. 14E shows the molded connection illustrated in FIG. 14D with thecomponents assembled;

FIG. 14F shows a cut-away view of the molded connection illustrated inFIGS. 14D and 14E;

FIG. 14G shows an exploded view of a fastener connection suitable formounting an integration plate onto an implant;

FIG. 14H shows the fastener connection illustrated in FIG. 14G with thecomponents assembled;

FIG. 14I shows a cut-away view of the fastener connection illustrated inFIGS. 14G and 14H;

FIG. 14J shows an exploded view of an undercut retention connectionsuitable for mounting an integration plate onto an implant;

FIG. 14K shows the undercut retention connection illustrated in FIG. 14Jwith the components assembled;

FIG. 14L shows a cut-away view of the undercut retention connectionillustrated in FIGS. 14J and 14K;

FIG. 14M shows an exploded view of adhesive-undercut connection suitablefor mounting an integration plate onto an implant;

FIG. 14N shows the adhesive-undercut connection illustrated in FIG. 14Mwith the components assembled;

FIG. 14O shows a cut-away view of the adhesive-undercut connectionillustrated in FIGS. 14M and 14N;

FIG. 14P shows an exploded view of a press-fit connection suitable formounting an integration plate onto an implant;

FIG. 14Q shows the press-fit connection illustrated in FIG. 14P with thecomponents assembled;

FIG. 14R shows a cut-away view of the press-fit connection illustratedin FIGS. 14P and 14Q;

FIG. 14S shows an exploded view of a snap-fit connection suitable formounting an integration plate onto an implant;

FIG. 14T shows the snap-fit connection illustrated in FIG. 14S with thecomponents assembled;

FIG. 14U shows a cut-away view of the snap-fit connection illustrated inFIGS. 14S and 14T;

FIG. 14V shows an exploded view of an internal molded connectionsuitable for mounting an integration plate onto an implant;

FIG. 14W shows the internal molded connection illustrated in FIG. 14Vwith the components assembled;

FIG. 14X shows a cut-away view of the internal molded connectionillustrated in FIGS. 14V and 14W;

FIG. 15A shows an example of a roughened topography capable of beingcreated by coating a material onto the surface of an implant;

FIG. 15B shows a flat implant surface capable of receiving a coatedroughened topography;

FIG. 15C shows a cut-away view of the coated roughened topographyillustrated in FIG. 15A;

FIG. 15D shows an example of a roughened topography capable of beingcreated by pressing a flexible foil onto the surface of an implant;

FIG. 15E shows an exploded view of the flexible foil and implantsurface;

FIG. 15F shows an exploded side view of the flexible foil and implantillustrated in FIG. 15E;

FIG. 16A shows a side view of the representation of an integration platehaving posts with one groove for mating with a corresponding tonguestructure in an implant hole;

FIG. 16B shows a bottom view of the representation illustrated in FIG.16A;

FIG. 16C shows an example of a tongue-and-groove connection suitable formounting an integration plate onto an implant;

FIG. 16D shows a close-up view of the tongue-and-groove connectionillustrated in FIG. 16C;

FIG. 16E shows a side view of a representation of an integration platehaving posts with three grooves for mating with a corresponding tonguestructure in an implant hole;

FIG. 16F shows a bottom view of the representation illustrated in FIG.16E;

FIG. 16G shows an example of a multiple tongue-and-groove connectionsuitable for mounting an integration plate onto an implant;

FIG. 16H shows a close-up view of the multiple tongue-and-grooveconnection illustrated in FIG. 16G;

FIG. 16I shows a side view of a representation of an integration platehaving posts with a rounded tongue structure for mating with acorresponding groove in an implant hole;

FIG. 16J shows a bottom view of the representation illustrated in FIG.16I;

FIG. 16K shows an example of a rounded tongue-and-groove connectionsuitable for mounting an integration plate onto an implant;

FIG. 16L shows a close-up view of the rounded tongue-and-grooveconnection illustrated in FIG. 16K;

FIG. 16M shows a side view of a representation of an integration platehaving posts with a diamond-shaped tongue structure for mating with acorresponding diamond-shaped groove in an implant hole;

FIG. 16N shows a bottom view of the representation illustrated in FIG.16M;

FIG. 16O shows an example of a diamond-shaped tongue-and-grooveconnection suitable for mounting an integration plate onto an implant;

FIG. 16P shows a close-up view of the diamond-shaped tongue-and-grooveconnection illustrated in FIG. 16O;

FIG. 16Q shows a side view of a representation of an integration platehaving posts with a threaded tongue structure for mating with acorresponding threaded groove in an implant hole;

FIG. 16R shows a bottom view of the representation illustrated in FIG.16Q;

FIG. 16S shows an example of a threaded tongue-and-groove connectionsuitable for mounting an integration plate onto an implant;

FIG. 16T shows a close-up view of the threaded tongue-and-grooveconnection illustrated in FIG. 16S;

FIG. 16U shows a side view of a representation of an integration platehaving posts with a plurality of a disc-shaped structures for matingwith corresponding grooves in an implant hole;

FIG. 16V shows a bottom view of the representation illustrated in FIG.16U;

FIG. 16W shows an example of a disc-shaped tongue and groove connectionsuitable for mounting an integration plate onto an implant;

FIG. 16X shows a close-up view of the disc-shaped tongue and grooveconnection illustrated in FIG. 16W;

FIG. 16Y shows a cut-away view of the disc-shaped tongue and grooveconnection illustrated in FIGS. 16W and 16X;

FIG. 17A shows a side view of a representation of an integration platehaving posts with vertically-oriented star-shaped tongue-and-groovestructures for mating with corresponding vertically-orientedtongue-and-groove structures in an implant hole;

FIG. 17B shows a bottom view of the representation illustrated in FIG.17A;

FIG. 17C shows an example of a star-shaped tongue-and-groove connectionsuitable for mounting an integration plate onto an implant;

FIG. 17D shows a close-up view of the star-shaped tongue-and-grooveconnection illustrated in FIG. 17C;

FIG. 18A shows an oval-shaped implant with a protruding anti-expulsionedge;

FIG. 18B shows a close-up view of the protruding anti-expulsion edge ofthe implant illustrated in FIG. 18A;

FIG. 18C shows a rectangular-shaped implant with a protrudinganti-expulsion edge oriented toward the posterior portion;

FIG. 18D shows a close-up view of the protruding anti-expulsion edge ofthe implant illustrated in FIG. 18C;

FIG. 18E shows a perspective view of a curved-shaped implant with aprotruding anti-expulsion edge oriented toward the posterior portion;

FIG. 18F shows a close-up view of the protruding anti-expulsion edge ofthe implant perspective illustrated in FIG. 18E;

FIG. 18G shows another perspective view of the implant illustrated inFIG. 18E;

FIG. 18H shows a close-up view of the protruding anti-expulsion edge ofthe implant illustrated in FIG. 18G;

FIG. 18I shows a perspective view of a rectangular-shaped implant with aprotruding anti-expulsion edge oriented toward one of the lateral sides;

FIG. 18J shows another perspective view of the implant illustrated inFIG. 18I;

FIG. 18K shows a close-up view of the protruding anti-expulsion edge ofthe implant illustrated in FIG. 18I;

FIG. 18L shows a perspective view of a cervical implant with aprotruding anti-expulsion edge;

FIG. 18M shows a close-up view of the protruding anti-expulsion edge ofthe implant illustrated in FIG. 18L;

FIG. 19A shows a cut-away view of an implant with an integration platehaving a protruding anti-expulsion edge;

FIG. 19B shows a smooth joint between the integration plate and theimplant illustrated in FIG. 19A;

FIG. 20A shows a side view of an integration plate having a protrudinganti-expulsion edge;

FIG. 20B shows a sharp edge configuration of the posterior edge of theintegration plate illustrated in FIG. 20A;

FIG. 20C shows a chamfered edge configuration of the posterior edge ofan integration plate;

FIG. 20D shows a radiused edge configuration of the posterior edge of anintegration plate;

FIG. 21 shows an example of an integration plate lordotic angle; and

FIG. 22 shows a example of an anti-expulsion edge angle.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be especially suited forplacement between adjacent human vertebral bodies. The implants of theinvention may be used in procedures such as Anterior Lumbar InterbodyFusion (ALIF), Posterior Lumbar Interbody Fusion (PLIF), TransforaminalLumbar Interbody Fusion (TLIF), and cervical fusion. Certain embodimentsdo not extend beyond the outer dimensions of the vertebral bodies.

The ability to achieve spinal fusion is directly related to theavailable vascular contact area over which fusion is desired, thequality and quantity of the fusion mass, and the stability of theinterbody spinal implant. Interbody spinal implants, as now taught,allow for improved seating over the apophyseal rim of the vertebralbody. Still further, interbody spinal implants, as now taught, betterutilize this vital surface area over which fusion may occur and maybetter bear the considerable biomechanical loads presented through thespinal column with minimal interference with other anatomical orneurological spinal structures. Even further, interbody spinal implants,according to certain aspects of the invention, allow for improvedvisualization of implant seating and fusion assessment. Interbody spinalimplants, as now taught, may also facilitate osteointegration with thesurrounding living bone.

Anterior interbody spinal implants in accordance with certain aspects ofthe invention can be preferably made of a durable material such asstainless steel, stainless steel alloy, titanium, or titanium alloy, butcan also be made of other durable materials such as, but not limited to,polymeric, ceramic, and composite materials. For example, certainembodiments of the invention may be comprised of a biocompatible,polymeric matrix reinforced with bioactive fillers, fibers, or both.Certain embodiments of the invention may be comprised of urethanedimethacrylate (DUDMA)/tri-ethylene glycol dimethacrylate (TEDGMA)blended resin and a plurality of fillers and fibers including bioactivefillers and E-glass fibers. Durable materials may also consist of anynumber of pure metals, metal alloys, or both. Titanium and its alloysare generally preferred for certain embodiments of the invention due totheir acceptable, and desirable, strength and biocompatibility. In thismanner, certain embodiments of the present interbody spinal implant mayhave improved structural integrity and may better resist fracture duringimplantation by impact. Interbody spinal implants, as now taught, maytherefore be used as a distractor during implantation.

Referring now to the drawing, in which like reference numbers refer tolike elements throughout the various figures that comprise the drawing,FIG. 1 shows a perspective view of a first embodiment of the interbodyspinal implant 1 especially well adapted for use in an ALIF procedure.

The interbody spinal implant 1 includes a body having a top surface 10,a bottom surface 20, opposing lateral sides 30, and opposing anterior 40and posterior 50 portions. One or both of the top surface 10 and thebottom surface 20 has a roughened topography 80. The roughenedtopography 80, however, is distinct from the teeth provided on thesurfaces of some conventional devices.

In some aspects, the interbody spinal implant 1 is substantially hollowand has a generally oval-shaped transverse cross-sectional area withsmooth, rounded, or both smooth and rounded lateral sides 30 andposterior-lateral corners 52. A substantially hollow implant 1 includesan implant 1 having at least about 33% of the interior volume of theimplant 1 vacant. The implant 1 includes at least one vertical aperture60 that extends the entire height of the implant body. The verticalaperture 60 may further define a transverse rim 100 having a greaterposterior portion thickness 55 than an anterior portion thickness 45.

In at least one embodiment, the opposing lateral sides 30 and theanterior portion 40 have a rim thickness 45 of about 5 mm, while theposterior portion 50 has a rim thickness 55 of about 7 mm. Thus, the rimposterior portion thickness 55 may allow for better stress sharingbetween the implant 1 and the adjacent vertebral endplates and helps tocompensate for the weaker posterior endplate bone. In some aspects, thetransverse rim 100 has a generally large surface area and contacts thevertebral endplate. The transverse rim 100 may act to better distributecontact stresses upon the implant 1, and hence minimize the risk ofsubsidence while maximizing contact with the apophyseal supportive bone.It is also possible for the transverse rim 100 to have a substantiallyconstant thickness (e.g., for the anterior portion thickness 45 to besubstantially the same as the posterior portion thickness 55) or for theposterior portion 50 to have a rim thickness 55 less than that of theopposing lateral sides 30 and the anterior portion 40. Some studies havechallenged the characterization of the posterior endplate bone asweaker.

It is generally believed that the surface of an implant determines itsultimate ability to integrate into the surrounding living bone. Withoutbeing limited to any particular theory or mechanism of action, it isbelieved that the cumulative effects of at least implant composition,implant surface energy, and implant surface roughness play a major rolein the biological response to, and osteointegration of, an implantdevice. Thus, implant fixation may depend, at least in part, on theattachment and proliferation of osteoblasts and like-functioning cellsupon the implant surface. Still further, it appears that these cellsattach more readily to relatively rough surfaces rather than smoothsurfaces. In this manner, a surface may be bioactive due to its abilityto facilitate cellular attachment and osteointegration. The surfaceroughened topography 80 may better promote the osteointegration of theimplant 1. The surface roughened topography 80 may also better grip thevertebral endplate surfaces and inhibit implant migration of the implant1 upon placement and seating in a patient.

Accordingly, the implant 1 further includes the roughened topography 80on at least a portion of its top 10 and bottom 20 surfaces for grippingadjacent bone and inhibiting migration of the implant 1. FIG. 1 showsroughened topography 80 on an embodiment of the implant 1.

The roughened topography 80 may be obtained through a variety oftechniques including, without limitation, chemical etching, shotpeening, plasma etching, laser etching, or abrasive blasting (such assand or grit blasting). In at least one embodiment, the interbody spinalimplant 1 may be comprised of titanium, or a titanium alloy, having thesurface roughened topography 80. The surfaces of the implant 1 arepreferably bioactive.

In a preferred embodiment of the invention, the roughened topography 80is obtained via the repetitive masking and chemical or electrochemicalmilling processes described in U.S. Pat. No. 5,258,098; No. 5,507,815;No. 5,922,029; and No. 6,193,762. Each of these patents is incorporatedin this document by reference. Where the invention employs chemicaletching, the surface is prepared through an etching process whichutilizes the random application of a maskant and subsequent etching ofthe metallic substrate in areas unprotected by the maskant. This etchingprocess is repeated a number of times as necessitated by the amount andnature of the irregularities required for any particular application.Control of the strength of the etchant material, the temperature atwhich the etching process takes place, and the time allotted for theetching process allow fine control over the resulting surface producedby the process. The number of repetitions of the etching process canalso be used to control the surface features.

By way of example, an etchant mixture of nitric acid (HNO₃) andhydrofluoric (HF) acid may be repeatedly applied to a titanium surfaceto produce an average etch depth of about 0.53 mm. Interbody spinalimplants 1, in accordance with some preferred embodiments of theinvention, may be comprised of titanium, or a titanium alloy, having anaverage surface roughness of about 100 μm. Surface roughness may bemeasured using a laser profilometer or other standard instrumentation.

In another example, chemical modification of the titanium implantsurfaces can be achieved using HF and a combination of hydrochloric acidand sulfuric acid (HCl/H₂SO₄). In a dual acid etching process, the firstexposure is to HF and the second is to HCl/H₂SO₄. Chemical acid etchingalone of the titanium implant surface has the potential to greatlyenhance osteointegration without adding particulate matter (e.g.,hydroxyapatite) or embedding surface contaminants (e.g., gritparticles).

The implant 1 may be shaped to reduce the risk of subsidence, andimprove stability, by maximizing contact with the apophyseal rim ofvertebral endplates. Embodiments may be provided in a variety ofanatomical footprints having a medial-lateral width ranging from about32 mm to about 44 mm. An interbody spinal implant 1 generally does notrequire extensive supplemental or obstructive implant instrumentation tomaintain the prepared disc space during implantation. Thus, theinterbody spinal implant 1 and associated implantation methods allow forlarger-sized implants as compared with other size-limited interbodyspinal implants known in the art. This advantage allows for greatermedial-lateral width and correspondingly greater contact with theapophyseal rim. The implant 1 may also include an anti-expulsion edge 8as described in more detail below.

As illustrated in FIG. 1, the implant 1 has an opening 90 in theanterior portion 40. In one embodiment the posterior portion 50 has asimilarly shaped opening 90. In some aspects, only the anterior portion40 has the opening 90 while the posterior portion 50 has an alternativeopening 92 (which may have a size and shape different from the opening90).

The opening 90 has a number of functions. One function is to facilitatemanipulation of the implant 1 by the caretaker. Thus, the caretaker mayinsert a surgical tool into the opening 90 and, through the engagementbetween the surgical tool and the opening 90, manipulate the implant 1.The opening 90 may be threaded to enhance the engagement.

The implant 1 may further include at least one transverse aperture 70that extends the entire transverse length of the implant body. The atleast one transverse aperture 70 may provide improved visibility of theimplant 1 during surgical procedures to ensure proper implant placementand seating, and may also improve post-operative assessment of implantfusion. Still further, the substantially hollow area defined by theimplant 1 may be filled with cancellous autograft bone, allograft bone,DBM, porous synthetic bone graft substitute, BMP, or combinations ofthese materials (collectively, bone graft materials), to facilitate theformation of a solid fusion column within the spine of a patient.

Certain embodiments of the invention are particularly suited for useduring interbody spinal implant procedures (or vertebral bodyreplacement procedures) and may act as a final distractor duringimplantation, thus minimizing the instrument load upon the surgeon. Forexample, in such a surgical procedure, the spine may first be exposedvia an anterior approach and the center of the disc space identified.The disc space is then initially prepared for implant insertion byremoving vertebral cartilage. Soft tissue and residual cartilage maythen also be removed from the vertebral endplates.

Vertebral distraction may be performed using trials of various-sizedembodiments of the interbody spinal implant 1. The determinatively sizedinterbody implant 1 may then be inserted in the prepared disc space forfinal placement. The distraction procedure and final insertion may alsobe performed under fluoroscopic guidance. The substantially hollow areawithin the implant body may optionally be filled, at least partially,with bone fusion-enabling materials such as, without limitation,cancellous autograft bone, allograft bone, DBM, porous synthetic bonegraft substitute, BMP, or combinations of those materials. Such bonefusion-enabling material may be delivered to the interior of theinterbody spinal implant 1 using a delivery device mated with theopening 90 in the anterior portion 40 of the implant 1. The interbodyspinal implant 1 may be generally larger than those currently known inthe art, and therefore have a correspondingly larger hollow area whichmay deliver larger volumes of fusion-enabling bone graft material. Thebone graft material may be delivered such that it fills the full volume,or less than the full volume, of the implant interior and surroundingdisc space appropriately.

As noted above, FIG. 1 shows a perspective view of one embodiment of theinvention, the interbody spinal implant 1, which is especially welladapted for use in an ALIF procedure. Other embodiments of the inventionare better suited for PLIF, TLIF, or cervical fusion procedures.Specifically, FIGS. 2 and 3 show perspective views, from the front andrear, respectively, of an embodiment of an interbody spinal implant 101especially well adapted for use in a PLIF procedure. The interbodyspinal implant 101 includes a body having a top surface 110, a bottomsurface 120, opposing lateral sides 130, and opposing anterior 140 andposterior 150 portions. One or both of the top surface 110 and thebottom surface 120 has a roughened topography 180 for gripping adjacentbone and inhibiting migration of the implant 101.

Certain embodiments of the interbody spinal implant 101 aresubstantially hollow and have a generally rectangular shape with smooth,rounded, or both smooth and rounded lateral sides and anterior-lateralcorners. As best shown in FIG. 3, the anterior portion 140 may have atapered nose 142 to facilitate insertion of the implant 101. To furtherfacilitate insertion, the implant 101 has chamfers 106 at the corners ofits posterior portion 150. The chamfers 106 prevent the implant 101 fromcatching upon insertion, risking potential damage such as severednerves, while still permitting the implant 101 to have an anti-expulsionedge 108.

The implant 101 includes at least one vertical aperture 160 that extendsthe entire height of the implant body. The vertical aperture 160 furtherdefines a transverse rim 200. The size and shape of the verticalaperture 160 are carefully chosen to achieve a preferable designtradeoff for the particular application envisioned for the implant 101.Specifically, the vertical aperture 160 seeks to maximize the surfacearea of the top surface 110 and the bottom surface 120 availableproximate the anterior 140 and posterior 150 portions while maximizingboth radiographic visualization and access to the bone graft materialtoward the center of the top 110 and bottom 120 surfaces. Thus, the sizeand shape of the vertical aperture 160 are predetermined by theapplication to which the implant 101 will be used.

In the particular example shown in FIGS. 2 and 3, the width of theimplant 101 between the two lateral sides 130 is approximately 9 mm. Theshape of the vertical aperture 160 approximates, in cross section, thatof an American football. The center of the vertical aperture 160, whichdefines the maximum width of the vertical aperture 160, is about 5 mm.Thus, the rim thickness 200 on either side of the vertical aperture 160adjacent the center of the vertical aperture 160 is about 2 mm. Thesedimensions permit ample engagement between the bone graft materialcontained within the implant 101 and bone.

The vertical aperture 160 tapers from its center to its ends along alongitudinal distance of about 7.75 mm (thus, the total length of thevertical aperture 160 is about 15.5 mm). This shape leaves intact muchof the rim thickness 200 in the areas around the ends of the verticalaperture 160. These areas may allow for better stress sharing betweenthe implant 101 and the adjacent vertebral endplates. Thus, thetransverse rim 200 has a generally large surface area and contacts thevertebral endplate.

As illustrated in FIG. 2, the implant 101 has an opening 190 in theposterior portion 150. The opening 190 has a number of functions. Onefunction is to facilitate manipulation of the implant 101 by thecaretaker. Thus, the caretaker may insert a surgical tool into theopening 190 and, through the engagement between the surgical tool andthe opening 190, manipulate the implant 101. The opening 190 may bethreaded to enhance the engagement.

The implant 101 may also have an Implant Holding Feature (IHF) 194instead of or in addition to the opening 190. As illustrated in FIG. 2,the IHF 194 is located proximate the opening 190 in the posteriorportion 150. In this particular example, the IHF 194 is a U-shapednotch. Like the opening 190, the IHF 194 has a number of functions, oneof which is to facilitate manipulation of the implant 101 by thecaretaker. Other functions of the opening 190 and the IHF 194 are toincrease visibility of the implant 101 during surgical procedures and toenhance engagement between bone graft material and adjacent bone.

The implant 101 may further include at least one transverse aperture170. Like the vertical aperture 160, the size and shape of thetransverse aperture 170 are carefully chosen (and predetermined) toachieve a preferable design tradeoff for the particular applicationenvisioned for the implant 101. Specifically, the transverse aperture170 should have minimal dimensions to maximize the strength andstructural integrity of the implant 101. On the other hand, thetransverse aperture 70 should have maximum dimensions to (a) improve thevisibility of the implant 101 during surgical procedures to ensureproper implant placement and seating, and to improve post-operativeassessment of implant fusion, and (b) to facilitate engagement betweenbone graft material and adjacent bone. The substantially hollow areadefined by the implant 101 may be filled with bone graft materials tofacilitate the formation of a solid fusion column within the spine of apatient.

As shown in FIGS. 2 and 3, the transverse aperture 170 extends theentire transverse length of the implant body and nearly the entireheight of the implant body. Thus, the size and shape of the transverseaperture 170 approach the maximum possible dimensions for the transverseaperture 170.

The transverse aperture 170 may be broken into two, separate sections byan intermediate wall 172. The section of the transverse aperture 170proximate the IHF 194 is substantially rectangular in shape; the othersection of the transverse aperture 170 has the shape of a curved arch.Other shapes and dimensions are suitable for the transverse aperture170. In particular, all edges of the transverse aperture 170 may berounded, smooth, or both. The intermediate wall 172 may be made of thesame material as the remainder of the implant 101 (e.g., metal), or itmay be made of another material (e.g., PEEK) to form a composite implant101. The intermediate wall 172 may offer one or more of severaladvantages, including reinforcement of the implant 101 and improved bonegraft containment.

The embodiment of the invention illustrated in FIGS. 2 and 3 isespecially well suited for a PLIF surgical procedure. TLIF surgery isdone through the posterior (rear) part of the spine and is essentiallylike an extended PLIF procedure. The TLIF procedure was developed inresponse to some of the technical problems encountered with a PLIFprocedure. The main difference between the two spine fusion proceduresis that the TLIF approach to the disc space is expanded by removing oneentire facet joint; a PLIF procedure is usually done on both sides byonly taking a portion of each of the paired facet joints.

By removing the entire facet joint, visualization into the disc space isimproved and more disc material can be removed. Such removal should alsoprovide for less nerve retraction. Because one entire facet is removed,the TLIF procedure is only done on one side: removing the facet jointson both sides of the spine would result in too much instability. Withincreased visualization and room for dissection, one or both of a largerimplant and more bone graft can be used in the TLIF procedure.Theoretically, these advantages can allow the spine surgeon to distractthe disc space more and realign the spine better (re-establish thenormal lumbar lordosis).

Although the TLIF procedure offers some improvements over a PLIFprocedure, the anterior approach in most cases still provides the bestvisualization, most surface area for healing, and the best reduction ofany of the approaches to the disc space. These advantages must beweighed, however, against the increased morbidity (e.g., unwantedaftereffects and postoperative discomfort) of a second incision.Probably the biggest determinate in how the disc space is approached isthe comfort level that the spine surgeon has with an anterior approachfor the spine fusion surgery. Not all spine surgeons are comfortablewith operating around the great vessels (aorta and vena cava) or haveaccess to a skilled vascular surgeon to help them with the approach.Therefore, choosing one of the posterior approaches for the spine fusionsurgery is often a more practical solution.

The embodiment of the invention illustrated in FIGS. 4 and 5 isespecially well suited when the spine surgeon elects a TLIF procedure.Many of the features of the implant 101 a illustrated in FIGS. 4 and 5are the same as those of the implant 101 illustrated in FIGS. 2 and 3.Therefore, these features are given the same reference numbers, with theaddition of the letter “a,” and are not described further.

There are several differences, however, between the two embodiments. Forexample, unlike the substantially rectangular shape of the implant 101,the implant 101 a has a curved shape. Further, the chamfers 106 andanti-expulsion edge 108 of the implant 101 are replaced by curves orrounded edges for the implant 101 a. Still further, the TLIF procedureoften permits use of a larger implant 101 a which, in turn, may affectthe size and shape of the predetermined vertical aperture 160 a.

The substantially constant 9 mm width of the transverse rim 200 of theimplant 101 is replaced with a larger, curved transverse rim 200 a. Thewidth of the transverse rim 200 a is 9 mm in the regions adjacent theanterior 140 a and posterior 150 a portions. That width graduallyincreases to 11 mm, however, near the center of the transverse rim 200a. The additional real estate provided by the transverse rim 200 a(relative to the transverse rim 200) allows the shape of the verticalaperture 160 a to change, in cross section, from approximating afootball to approximating a boomerang. Maintaining the thickness of thetransverse rim 200 a on either side of the vertical aperture 160 aadjacent the center of the vertical aperture 160 a at about 2 mm,similar to the dimensions of the implant 101, the center of the verticalaperture 160 a, which defines the maximum width of the vertical aperture160 a, is increased (from 5 mm for the implant 101) to about 7 mm.

The implant 101 a may also have a lordotic angle to facilitatealignment. The lateral side 130 a depicted at the top of the implant 101a is preferably generally greater in height than the opposing lateralside 130 a. Therefore, the implant 101 a may better compensate for thegenerally less supportive bone found in certain regions of the vertebralendplate.

As shown in FIG. 4, the transverse aperture 170 a extends the entiretransverse length of the implant body and nearly the entire height ofthe implant body. FIG. 5 highlights an alternative transverse aperture170 a. As illustrated in FIG. 5, the transverse aperture 170 a is brokeninto two, separate sections by an intermediate wall 172 a. Thus, thedimensions of the transverse aperture 170 a shown in FIG. 5 are muchsmaller than those for the transverse aperture 170 a shown in FIG. 4.The two sections of the alternative transverse aperture 170 a are eachillustrated as substantially rectangular in shape and extending nearlythe entire height of the implant body; other sizes and shapes arepossible for one or both sections of the alternative transverse aperture170 a.

The intermediate wall 172 a may be made of the same material as theremainder of the implant 101 a (e.g., metal), or it may be made ofanother material (e.g., PEEK) to form a composite implant 101 a. It isalso possible to extend the intermediate wall 172 a, whether made ofmetal, PEEK, ultra-high molecular weight polyethylene (UHMWPE), oranother material, to eliminate entirely the transverse aperture 170 a.Given the reinforcement function of the intermediate wall 172 a, thelength of the vertical aperture 160 a can be extended (as shown in FIG.5) beyond the top surface 110 a and into the anterior portion 140 a ofthe implant 101 a.

The top surface 110 a of the implant 101 a need not include theroughened topography 180 a. This difference permits the implant 101 a,at least for certain applications, to be made entirely of a non-metalmaterial. Suitable materials of construction for the implant 101 a ofsuch a design (which would not be a composite) include PEEK, hedrocel,UHMWPE, other radiolucent soft plastics, and additional materials aswould be known town artisan.

The embodiments of the invention described above are best suited for oneor more of the ALIF, PLIF, and TLIF surgical procedures. Anotherembodiment of the invention is better suited for cervical fusionprocedures. This embodiment is illustrated in FIGS. 6 and 7 as theinterbody spinal implant 201.

Because there is not a lot of disc material between the vertebral bodiesin the cervical spine, the discs are usually not very large. The spaceavailable for the nerves is also not that great, however, which meansthat even a small cervical disc herniation may impinge on the nerve andcause significant pain. There is also less mechanical load on the discsin the cervical spine as opposed to the load that exists lower in thespine. Among others, these differences have ramifications for the designof the implant 201.

The implant 201 is generally smaller in size than the other implantembodiments. In addition, the lower mechanical load requirements imposedby the cervical application typically render a composite implantunnecessary. Therefore, the implant 201 is generally made entirely ofmetal (e.g., titanium) and devoid of other materials (e.g., PEEK).

With specific reference to FIG. 6, the implant 201 includes a bodyhaving a top surface 210, a bottom surface 220, opposing lateral sides230, and opposing anterior 240 and posterior 250 portions. One or bothof the top surface 210 and the bottom surface 220 has a roughenedtopography 280 for gripping adjacent bone and inhibiting migration ofthe implant 201. The implant 201 is substantially hollow and has agenerally oval shape with smooth, rounded, or both smooth and roundededges.

The implant 201 includes at least one vertical aperture 260 that extendsthe entire height of the implant body. The vertical aperture 260 furtherdefines a transverse rim 300. The size and shape of the verticalaperture 260 are carefully chosen to achieve a preferable designtradeoff for the particular application envisioned for the implant 201.Specifically, the vertical aperture 260 seeks to maximize the surfacearea of the top surface 210 and the bottom surface 220, to allow forbetter stress sharing between the implant 201 and the adjacent vertebralendplates, while maximizing access to the bone graft material providedwithin the implant 201. Thus, the size and shape of the verticalaperture 260 are predetermined by the application.

As illustrated in FIG. 6, the implant 201 has an opening 290 in theposterior portion 250. The opening 290 has a number of functions. Onefunction is to facilitate manipulation of the implant 201 by thecaretaker. Thus, the caretaker may insert a surgical tool into theopening 290 and, through the engagement between the surgical tool andthe opening 290, manipulate the implant 201. The opening 290 may bethreaded to enhance the engagement.

The implant 201 may further include at least one transverse aperture270. Like the vertical aperture 260, the size and shape of thetransverse aperture 270 are carefully chosen (and predetermined) toachieve a preferable design tradeoff for the particular applicationenvisioned for the implant 201. For example, as shown in FIG. 6, thetransverse aperture 270 may extend the entire transverse length of theimplant body and nearly the entire height of the implant body. Thus, thesize and shape of the transverse aperture 270 approach the maximumpossible dimensions for the transverse aperture 270.

As illustrated in FIG. 6, the implant 201 may be provided with a solidrear wall 242. The rear wall 242 extends the entire width of the implantbody and nearly the entire height of the implant body. Thus, the rearwall 242 essentially closes the anterior portion 240 of the implant 201.The rear wall 242 may offer one or more of several advantages, includingreinforcement of the implant 201 and improved bone graft containment. Inthe cervical application, it may be important to prevent bone graftmaterial from entering the spinal canal.

Alternative shapes for the implant 201 are possible. As illustrated inFIG. 7, for example, the implant 201 may have a generally box shapewhich gives the implant 201 increased cortical bone coverage. Like theimplant 201 shown in FIG. 6, the implant 201 shown in FIG. 7 has acurved transverse rim 300 in the area of the anterior portion 240. Theshape of the posterior portion 250 of the implant 201 is substantiallyflat, however, and the shape of the transverse rim 300 in the area ofthe posterior portion 250 is substantially square. Thus, the posteriorportion 250 provides a face that can receive impact from a tool, such asa surgical hammer, to force the implant 201 into position.

The implant 201 may also have a lordotic angle to facilitate alignment.As illustrated in FIGS. 6 and 7, the anterior portion 240 is preferablygenerally greater in height than the posterior portion 250. Therefore,the implant 201 may better compensate for the generally less supportivebone found in certain regions of the vertebral endplate. As an example,four degrees of lordosis may be built into the implant 201 to helprestore balance to the spine.

Certain embodiments of the implant 1, 101, 101 a, and 201 are generallyshaped (i.e., made wide) to maximize contact with the apophyseal rim ofthe vertebral endplates. They are designed to be impacted between theendplates, with fixation to the endplates created by an interference fitand annular tension. Thus, the implants 1, 101, 101 a, and 201 areshaped and sized to spare the vertebral endplates and leave intact thehoop stress of the endplates. A wide range of sizes are possible tocapture the apophyseal rim, along with a broad width of the peripheralrim, especially in the posterior region. It is expected that suchdesigns will lead to reduced subsidence. As much as seven degrees oflordosis (or more) may be built into the implants 1, 101, 101 a, and 201to help restore cervical balance.

When endplate-sparing spinal implant 1, 101, 101 a, and 201 seats in thedisc space against the apophyseal rim, it should still allow fordeflection of the endplates like a diaphragm. This means that,regardless of the stiffness of the spinal implant 1, 101, 101 a, and201, the bone graft material inside the spinal implant 1, 101, 101 a,and 201 receives load, leading to healthy fusion. The vertical load inthe human spine is transferred though the peripheral cortex of thevertebral bodies. By implanting an apophyseal-supporting inter-bodyimplant 1, 101, 101 a, and 201, the natural biomechanics may be betterpreserved than for conventional devices. If this is true, the adjacentvertebral bodies should be better preserved by the implant 1, 101, 101a, and 201, hence reducing the risk of adjacent segment issues.

In addition, the dual-acid etched roughened topography 80, 180, 180 a,and 280 of the top surface 30, 130, 130 a, and 230 and the bottomsurface 40, 140, 140 a, and 240 along with the broad surface area ofcontact with the end-plates, is expected to yield a high pull-out forcein comparison to conventional designs. As enhanced by the sharp edges 8and 108, a pull-out strength of up to 3,000 nt may be expected. Theroughened topography 80, 180, 180 a, and 280 creates a biological bondwith the end-plates over time, which should enhance the quality offusion to the bone. Also, the in-growth starts to happen much earlierthan the bony fusion. The center of the implant 1, 101, 101 a, and 201remains open to receive bone graft material and enhance fusion.Therefore, it is possible that patients might be able to achieve a fullactivity level sooner than for conventional designs.

The spinal implant 1, 101, 101 a, and 201 according to the inventionoffers several advantages relative to conventional devices. Suchconventional devices include, among others, ring-shaped cages made ofallograft bone material, threaded titanium cages, and ring-shaped cagesmade of PEEK or carbon fiber.

In some aspects, the implant 1, 101, 101 a, and 201 includes anintegration plate 82, 182, 182 a, and 282, for example, as shown in FIG.8A-FIG. 10 and FIG. 12. In addition, a lateral implant 301 having asubstantially rectangular shape may include an integration plate 382,for example, as shown in FIG. 11. The lateral implant 301 comprises thesame general features as the implant 1, 101, 101 a, and 201, including atop surface 310, a bottom surface 320, lateral sides 330, opposinganterior 340 and posterior 350 portions, an opening 390, as well as atleast one vertical aperture 360 that extends the entire height of theimplant body, and one or more transverse apertures 370 that extend theentire transverse length of the implant body.

The integration plate, shown in the drawings as component 82 (FIG. 8Aand FIG. 8B), 182 (FIG. 10), 182 a (FIG. 9), 382 (FIGS. 11), and 282(FIG. 12), respectively, includes the roughened surface topography 80,180, 180 a, 280, and 380, and is connectable to either or both of thetop surface 10, 110, 110 a, 210, and 310 or bottom surface 20, 120, 120a, 220, and 320. The integration plate 82, 182, 182 a, 282, and 382includes a top surface 81, 181, 181 a, 281, and 381; a bottom surface83, 183, 183 a, 283, and 383; an anterior portion 41, 141, 141 a, 241,and 341; a posterior portion 51, 151, 151 a, 251, and 351; and at leastone vertical aperture 61, 161, 161 a, 261, and 361. The anterior portion41, 141, 141 a, 241, and 341 preferably aligns with the anterior portion40, 140, 140 a, 240, and 340 of the main body of the implant 1, 101, 101a, 201, and 301, respectively, and the posterior portion 51, 151, 151 a,251, and 351 aligns with the posterior portion 50, 150, 150 a, 250, and350 of the main body of the implant 1, 101, 101 a, 201, and 301,respectively. The vertical aperture 61, 161, 161 a, 261, and 361preferably aligns with the vertical aperture 60, 160, 160 a, 260, and360 of the main body of the implant 1, 101, 101 a, 201, and 301,respectively. Thus, the integration plate vertical aperture 61, 161, 161a, 261, and 361 and the body vertical aperture 60, 160, 160 a, 260, and360 preferably comprise substantially the same shape.

The top surface 81, 181, 181 a, 281, and 381 of the integration plate82, 182, 182 a, 282, and 382 preferably comprises the roughenedtopography 80, 180, 180 a, 280, and 380. The bottom surface 83, 183, 183a, 283, and 383 of the integration plate 82, 182, 182 a, 282, and 382preferably comprises a reciprocal connector structure, such as aplurality of posts 84, 184, 184 a, 284, and 384 that align with andinsert into a corresponding connector structure such as a plurality ofholes 12, 112, 112 a, 212, and 312 on the top surface 10, 110, 110 a,210, and 310 and/or bottom surface 20, 120, 120 a, 220, and 320 of themain body of the implant 1, 101, 101 a, 201, and 301, respectively, andthus facilitate the connection between the integration plate 82, 182,182 a, 282, and 382 and the main body of the implant 1, 101, 101 a, 201,and 301. Thus, integration plates 82, 182, 182 a, 282, and 382 withdifferent sizes, shapes, or features may be used in connection with theimplant 1, 101, 101 a, 201, and 301, for example, to accommodateattributes of the spine of the patient to which the implant 1, 101, 101a, 201, and 301 is to be implanted. Among these different sizes, shapes,and features are lordotic angles; anti-expulsion edges 8, 108, 108 a,208, and 308; and anti-expulsion angles as described throughout thisspecification.

The implant 1, 101, 101 a, 201, and 301 is configured to receive theintegration plate 82, 182, 182 a, 282, and 382, respectively. Thus, forexample, the top surface 10, 110, 110 a, 210, and 310 and/or bottomsurface 20, 120, 120 a, 220, and 320 of the implant 1, 101, 101 a, 201,and 301 may be recessed, and comprise a plurality of holes 12, 112, 112a, 212, and 312 that mate with the plurality of posts 84, 184, 184 a,284, and 384 on the bottom surface 83, 183, 183 a, 283, and 383 of theintegration plate 82, 182, 182 a, 282, and 382. Thus, the plurality ofposts 84, 184, 184 a, 284, and 384 are inserted into the plurality ofholes 12, 112, 112 a, 212, and 312.

FIG. 8A and FIG. 8B show that the top surface 10 is recessed andcomprises a plurality of holes 12, but the recessed bottom surface 20and its holes 12 are not shown. FIG. 9 shows that the top surface 110 ais recessed and comprises a plurality of holes 112 a, but the recessedbottom surface 120 a and its holes 112 a are not shown. FIG. 10 showsthat the top surface 110 is recessed and comprises a plurality of holes112, but the recessed bottom surface 120 and its holes 112 are notshown. FIG. 11 shows that the top surface 310 is recessed and comprisesa plurality of holes 312, but the recessed bottom surface 320 and itsholes 312 are not shown. FIG. 12 shows that the top surface 210 isrecessed and comprises a plurality of holes 212, but the recessed bottomsurface 220 and its holes 212 are not shown. The recess may be at adepth D, and the recess depth D preferably is uniform throughout the topsurface 10, 110, 110 a, 210, and 310 and/or bottom surface 20, 120, 120a, 220, and 320.

The recess depth D preferably corresponds to a thickness T of theintegration plate 82, 182, 182 a, 282, and 382. Thus, in some aspects,the depth D and thickness T are the same so that once the integrationplate 82, 182, 182 a, 282, and 382 and body of the implant 1, 101, 101a, 201, and 301, respectively, are placed together, the top surface 10,110, 110 a, 210, and 310 and/or bottom surface 20, 120, 120 a, 220, and320 of the implant 1, 101, 101 a, 201, and 301 is substantially even, atleast at the seam/junction between the integration plate 82, 182, 182 a,282, and 382 and the top surface 10, 110, 110 a, 210, and 310 or bottomsurface 20, 210, 120 a, 220, and 320. In some embodiments, the posteriorportion 51, 151, 151 a, 251, and 351 and the anterior portion 41, 141,141 a, 241, and 341 of the integration plate 82, 182, 182 a, 282, and382 have different thicknesses such that the anterior portion 41, 141,141 a, 241, and 341 has a greater thickness than the thickness T of theposterior portion 51, 151, 151 a, 251, and 351. For example, as shown inFIG. 13A, the anterior portion 41 has a greater thickness T′ than thethickness T of the posterior portion 51.

The recess depth D, the thickness T, and the thickness T′ may eachindependently be from about 0.1 mm to about 10 mm. In preferred aspects,the recess depth D, the thickness T, and the thickness T′ may eachindependently be from about 1 mm to about 5 mm. Thus, for example,either the recess depth D, the thickness T, and the thickness T′ may beselected from about 0.1 mm, about 0.25 mm, about 0.5 mm, about 0.75 mm,about 1 mm, about 1.25 mm, about 1.5 mm, about 1.75 mm, about 2 mm,about 2.25 mm, about 2.5 mm, about 2.75 mm, about 3 mm, about 3.25 mm,about 3.5 mm, about 3.75 mm, about 4 mm, about 4.25 mm, about 4.5 mm,about 4.75 mm, about 5 mm, 5.5 mm, about 6 mm, about 6.5 mm, about 7 mm,about 75 mm, or about 8 mm.

Recessing the top surface 10, 110, 110 a, 210, and 310 or bottom surface20, 120, 120 a, 220, and 320 exposes a ridge 11, 111, 111 a, 211, and311 against which the anterior portion 41, 141, 141 a, 241, and 341,posterior portion 51, 151, 151 a, 251, and 251 or lateral side of theintegration plate 82, 182, 182 a, 282, and 382 may be seated whenbrought together with the implant 1, 101, 101 a, 201, and 301.

The integration plate 82, 182, 182 a, 282, and 382 may be used with animplant suitable for ALIF (e.g., implant 1, integration plate 82), PLIF(e.g., implant 101, integration plate 182), or TLIF fusion (e.g.,implant 101 a, integration plate 182 a); may be used with an implantsuitable for cervical fusion (e.g., implant 201, integration plate 282);and may be used with an implant suitable for lateral lumbar insertion(e.g., implant 301, integration plate 382). The integration plate 82,182, 182 a, 282, and 382 is preferably metal, and may be used with ametal implant. The metal integration plate 82, 182, 182 a, 282, and 382may also be used with a molded plastic or polymer implant, or acomposite implant. In some aspects, the integration plate 82, 182, 182a, 282, and 382 may also comprise a plastic, polymeric, or compositematerial.

The reciprocal connector such as the post 84, 184, 184 a, 284, and 384preferably is secured within the connector of the body such as the hole12, 112, 112 a, 212, and 312 to mediate the connection between theintegration plate 82, 182, 182 a, 282, and 382 and the implant 1, 101,101 a, 201, and 301. The connection should be capable of withstandingsignificant loads and shear forces when implanted in the spine of thepatient. The connection between the post 84, 184, 184 a, 284, and 384and the hole 12, 112, 112 a, 212, and 312 may comprise a friction fit.For example, FIG. 13A shows a cut-away side view of the implant 1 havingan integration plate 82 on the top 10 and bottom 20 portions, with theposts 84 inserted into the holes 12. FIG. 13B shows a close up view ofthe post 84 and hole 12 connection. In some aspects, the reciprocalconnector such as the post 84, 184, 184 a, 284, and 384 and theconnector of the body such as the hole 12, 112, 112 a, 212, and 312 haveadditional compatible structures and features to further strengthen theconnection between the integration plate 82, 182, 182 a, 282, and 382and the implant 1, 101, 101 a, 201, and 301. Non-limiting examples ofsuch structures and features are illustrated in FIGS. 14-17.

The structures and features may be on either or both of the integrationplate 82, 182, 182 a, 282, and 382 and the main body of the implant 1,101, 101 a, 201, and 301. In general, the structures include fasteners,compatibly shaped joints, compatibly shaped undercuts, and/or othersuitable connectors having different shapes, sizes, and configurations.For example, a fastener may include a pin, screw, bolt, rod, anchor,snap, clasp, clip, clamp, or rivet. In some aspects, an adhesive may beused to further strengthen any of the integration plate 82, 182, 182 a,282, and 382 and implant 1, 101, 101 a, 201, and 301 connectionsdescribed in this specification. An adhesive may comprise a cement,glue, polymer, epoxy, solder, weld, or other suitable binding material.

As shown in FIGS. 14A-14C, an integration plate 482 (shown in thedrawings as a box only for illustration purposes) having a roughenedsurface topography 480 may comprise one or more reciprocal connectorssuch as one or more posts 484 each having a bore 485 extending through ahorizontal plane. The post 484 is inserted into a connector such as ahole 412 through the implant 401 (also shown in the drawings as a boxonly for illustration purposes). A fastener 486, which may be a pin 486,is inserted through the bore 485 (FIG. 14A), thereby preventing the post484 from being disengaged from the hole 412 (FIG. 14B). In some aspects,the pin 486 is also threaded through a second bore 487 that passesthrough the walls of the implant 401 itself, although it is preferablethat the implant 401 does not include a second bore 487 through itswalls and that the bore 485 is accessible from the space inside of theimplant 401. It is to be understood that components numbered in the fourhundred series are shown for illustration purposes, and correspond tofeatures of each implant 1, 101, 101 a, 201, and 301; for example, post484 is representative of post 84, 184, 184 a, 284, and 384.

FIGS. 14D-F show another embodiment of the integration plate 482comprising a plurality of bores 485 present on and having an openingaccessible from the bottom surface 483 of the integration plate 482. Thebores 485 mate with a plurality of fasteners 486, which may compriserods 486 (FIG. 14D) integral with or otherwise attached to the topsurface 410 or bottom surface (not shown) of the implant 401. Forexample, the rods 486 may be molded as upward-facing extensions of thetop surface 410 (FIG. 14F). The rods 486 may be snap-fit into the bores485 through the opening (FIG. 14F), in which case the opening may beslightly smaller in width than the bores 485 and rods 486, though stillallowing the rods 486 to pass through the opening and into the bores485.

In some embodiments, such as those shown in FIGS. 14G-I, the integrationplate 482 comprises one or more bores 485 in a vertical plane, extendingthrough the integration plate 482, through which a fastener 486, whichmay be a screw or bolt 486, may be inserted. The screw or bolt 486 mayextend into a hole 412 extending at least partially into the implant401, and the hole 412 and screw or bolt 486 preferably comprisecompatible screw threads 415 (FIG. 14I). Tightening of the screw or bolt486 secures the integration plate 482 in place on the implant 401 (FIG.14H). In some aspects, for example, where the implant 401 is comprisedof a plastic or polymeric material, the hole 412 may not be present, andthe screw or bolt 486 may be screwed directly into the plastic orpolymeric material, with the screw threads tightly gripping the plasticor polymeric material to form the connection. The integration plate mayhave a roughened topography 480.

The bottom surface 483 of the integration plate 482 may compriseundercuts in shapes that form a tight junction with compatible shapes onthe implant 401. For example, as shown in FIGS. 14J-L, the bottomsurface 483 may comprise a dovetail joint, or bevel, or taper that fitswith a counterpart dovetail joint, bevel, or taper on the implant 401(FIG. 14L). The shape of each of the integration plate 482 undercuts(FIG. 14J) and counterpart undercuts on the implant 401 (FIG. 14L) aresuch that the connection forms a joint between the implant 401 andintegration plate 482, and that this joint is established and retainedwith a tight tolerance (FIG. 14K).

As shown in FIGS. 14M-O, the integration plate 482 comprising aplurality of bores 485 present on and having an opening accessible fromthe bottom surface 483 of the integration plate 482 may mate with aplurality of fasteners 486, which may comprise rod-shaped adhesives 486,or which may comprise rods 486 coated or otherwise impregnated with anadhesive (FIG. 14M). A rod-shaped adhesive 486 may comprise anhourglass-shaped cross section, with one side capable of being snap-fitinto the bores 485 through the opening, and with the other side capableof being snap-fit into bores 487 in the top surface 410 of the implant401. In this manner, the rod-shaped adhesive 486 may bridge the implant401 and integration plate 482 together as shown in FIG. 14O. In analternative embodiment, the implant 401 comprises rods 486 integral withor otherwise attached to the top surface 410 or bottom surface (notshown) of the implant 401, for example, as illustrated in FIG. 14D, andthese rods 486 may be coated with an adhesive that joins the rods 486together with the sidewalls of the bores 485 in the integration plate482.

An adhesive may directly join the integration plate 482 and the implant401 together. For example, the adhesive may be applied to the bottomsurface 483 of the integration plate 482 or the top surface 410 of theimplant 401, and each part bridged together with the adhesive (notillustrated). In some aspects, the bottom surface 483 of the integrationplate 482 may include undercuts in shapes that form a tight junctionwith compatible shapes on the implant 401. For example, an adhesive maybe applied to undercuts and joints as shown in FIG. 14J to strengthenthe connection between the integration plate 482 and the implant 401.FIGS. 14P-R show an alternative embodiment of undercuts on theintegration plate 482 that form a connection with corresponding cuts onthe implant 401, and an adhesive may be applied to strengthen thisconnection.

The integration plate 482 may be connected to the implant 401 with asnap-fit connection, for example, as shown in FIGS. 14S-U. Theintegration plate 482 may comprise one or more bores 485 extendingvertically through the integration plate 482, through which a fastener486, which may be a rivet, snap or snap button 486, may be inserted(FIG. 14S). The rivets 486, snaps 486, or snap buttons 486 may beintegral with or otherwise attached to the top surface 410 (FIG. 14S) orbottom surface (not shown) of the implant 401. For example, the rivets486, snaps 486, or snap buttons 486 may be molded as upward-facingextensions of the top surface 410 (FIG. 14U). In some preferred aspects,the rivets 486, snaps 486, or snap buttons 486 comprise a head portionwith a diameter slightly larger than and a shaft portion with a diameterslightly smaller than the diameter of the bores 485. In some preferredaspects, at least the head portion of the rivets 486, snaps 486, or snapbuttons 486 is fabricated of a material that allows the head portion tocompress slightly and pass through the bores 485 when the integrationplate 482 is pressed toward the implant 401, after which the headportion re-expands such that the rivets 486, snaps 486, or snap buttons486 cannot be disengaged from the bores 485 (FIG. 14T).

In some embodiments, an anchor plate 486 enhances the connection betweenthe posts 484 of the integration plate 482 and the holes 412 of theimplant 401, as shown in FIGS. 14V-14X. For example, the top surface 410of the implant 401 may be molded in a shape or configuration into whichan anchor plate 486 may be inserted (FIG. 14X), or the anchor plate 486may otherwise be adhered to the implant 401. The anchor plate 486 maycomprise one or more bores 485 through which the post 484 may passthrough (FIG. 14V). The integration plate 482, anchor plate 486, andimplant 401 may be pressed together to form a tight junction thatmaintains the connection of the integration plate 482 to the implant401.

The foregoing describes various non-limiting examples of how anintegration plate 82, 182, 182 a, 282, and 382 may be joined togetherwith an implant 1, 101, 101 a, 201, and 301. One non-limiting objectiveof this approach is to provide a roughened topography 80, 180, 180 a,280, and 380 to the surface of the implant 1, 101, 101 a, 201, and 301.The roughened topography 80, 180, 180 a, 280, and 380 can be establishedon the integration plate 82, 182, 182 a, 282, and 382 according to anysuitable methodology, including those described or exemplified in thisspecification. The roughened topography 80, 180, 180 a, 280, and 380 mayalso be provided by coating the implant 1, 101, 101 a, 201, and 301 orthe integration plate 82, 182, 182 a, 282, and 382 with a roughenedtopography material (e.g., FIGS. 15A-F).

For example, in some aspects, a material such as metal filings,shavings, or fine metal particles or powder, or fine plastic orpolymeric particles may be laid onto the top surface 10, 110, 110 a,210, and 310 or bottom surface 20, 120, 120 a, 220, and 320 of theimplant 1, 101, 101 a, 201, and 301 or onto the top surface 81, 181, 181a, 281, and 381 of the integration plate 82, 182, 182 a, 282, and 382according to any suitable method. In some aspects, an adhesive may beused to affix the material to the implant 1, 101, 101 a, 201, and 301 orintegration plate 82, 182, 182 a, 282, and 382. Plastic or polymericmaterials may be spray-coated, airlaid, or melt-blown onto the implant1, 101, 101 a, 201, and 301 or integration plate 82, 182, 182 a, 282,and 382. The materials may be adhered directly, for example, by at leastpartially melting the particles such that they fuse to the desiredsurface when they cool. Metal materials may be cold sprayed or thermalsprayed onto the implant 1, 101, 101 a, 201, and 301 or integrationplate 82, 182, 182 a, 282, and 382 according to any suitable technique.

FIGS. 15A-C show a non-limiting embodiment of a roughened topography 480coated onto the top surface 410 of the implant 401 (shown in thedrawings as a box only for illustration purposes). The roughenedtopography 480 may also be coated onto the bottom surface of the implant401 (not shown). The roughened topography 480 may be coated onto the topsurface 481 of the integration plate 482 (not shown).

In some alternative aspects, a backing 479 comprising a roughenedtopography 480 may be laid onto the top surface 410 of the implant 401as shown in FIGS. 15D-F. For example, the backing 479 may comprise afoil, mesh, screen, or other suitable material, preferably comprising ametal, that is sufficiently flexible such that it may conform to theshapes and contours of the top surface 410 of the implant 401 (FIG. 15Eand FIG. 15F). In this same manner, the backing 479 may be laid onto thetop surface 481 of the integration plate 482 (not shown). An adhesivemay be used to join the backing 479 to the top surface 410 of theimplant 401 or top surface 481 of the integration plate 482. The backing479 may be soldered, melted, or welded to the top surface 410 of theimplant 401 or top surface 481 of the integration plate 482.

A preferred connection between the integration plate 82, 182, 182 a,282, and 382 and the implant 1, 101, 101 a, 201, and 301 includes thepost 84, 184, 184 a, 284, and 384 and hole 12, 112, 112 a, 212, and 312connection, without additional fasteners required to maintain thisconnection, for example, through a friction fit. In some embodiments thepost 84, 184, 184 a, 284, and 384 and hole 12, 112, 112 a, 212, and 312include different interlocking joints to strengthen the connectionbetween them. These interlocking joints preferably include differentconfigurations of a basic tongue-and-groove joint, for example, as shownin FIGS. 16 and 17.

In some embodiments, an integration plate 482 (shown in the drawings asa box only for illustration purposes) having a roughened surfacetopography 480 may comprise one or more posts 484 (FIG. 16A), eachcomprising a groove 488 (FIG. 16A and FIG. 16B). The posts 484 mayinclude more than one groove 488, including two, three, four, five, six,seven, eight or more grooves 488. FIG. 16E and FIG. 16F show anon-limiting example of a post 484 with three groves 488.

Each groove 488 preferably mates with a corresponding tongue 489 in thehole 412 of the implant 401. For example, as shown in FIGS. 16C and 16D,each hole 412 may include one tongue 489 that forms a connection withone groove 488 in the post 484. The holes 412 may include more than onetongue 489, including two, three, four, five, six, seven, eight or moretongues 489. FIGS. 16G and 16H show a non-limiting example of each hole412 including three tongues 489.

When the integration plate 482 is pressed together with the implant 401(shown in the drawings as a box only for illustration purposes), thepost 484 is inserted into its corresponding hole 412, and each tongue489 is inserted into its corresponding groove 488. In this regard, it ispreferable that the material used to fabricate the tongue 489 issufficiently flexible to allow the wider portions of the post 484 thatflank each groove 488 to pass over the tongue 489 so that the tongue 489can fit within its groove 488, yet is sufficiently rigid to preventdisengagement of the tongue 489 from the groove 488 once the integrationplate 482 and implant 481 are together.

In some embodiments, the location of the tongue 489 and groove 488 onthe post 484 and hole 412 are reversed. For example, the tongue 489 maybe present on the post 484 and the groove 488 may be present on the hole412. FIGS. 16I-X show examples of a post 484 and hole 412 connection inwhich the post 484 comprises one or more tongues 489 that fit within oneor more grooves 488 in the sidewalls of the hole 412.

The tongue 489 may comprise a round shape (FIGS. 16I and 16J), and maythus mate with a groove 488 having a reciprocal round shape (FIGS. 16Kand 16L). The tongue 489 may comprise a triangular shape (FIGS. 16E and16F), and may thus mate with a groove 488 having a reciprocal triangularshape (FIGS. 16G and 16H). The tongue 489 may comprise a diamond shape(FIGS. 16M and 16N), and may thus mate with a groove 488 having areciprocal diamond shape (FIGS. 16O and 16P). The tongue 489 maycomprise a threaded shape (FIGS. 16O and 16R), and may thus mate with agroove 488 having a reciprocal threaded shape (FIGS. 16S and 16T). Thetongue 489 may comprise a disc shape (FIGS. 16U and 16V), and may thusmate with a groove 488 having a reciprocal disc shape (FIGS. 16W and16X). A cross-section of such a configuration is shown in FIG. 16Y.

Each hole may include one groove 488 that forms a connection with onetongue 489 on the post 484. The holes 412 may include more than onegroove 488, including two, three, four, five, six, seven, eight or moregrooves 488. The post 484 may include more than one tongue 489,including two, three, four, five, six, seven, eight or more tongues 489.

When the integration plate 482 is pressed together with the implant 401,the post 484 is inserted into its corresponding hole 412, and the tongue489 is inserted into its corresponding groove 488. It is preferable thatthe material out of which the tongue 489 is fabricated is sufficientlyflexible to allow the tongue 489 to pass over the wider portions of thehole 412 that flank each groove 488 so that the tongue 489 can fitwithin its groove 488, yet is sufficiently rigid to preventdisengagement of the tongue 489 from the groove 488 once the integrationplate 482 and implant 481 are together.

Whether on the post 484 or the hole 412, the tongue 489 and groove 488may comprise any suitable shape, and preferably, each has a shapecompatible with its counterpart. The shape may be regular or irregular.Each of the tongue 489 and groove 488 may comprise a substantiallyround, triangular, diamond, square, dovetail, or polygonal shape.Optionally, an adhesive may be used to further strengthen the connectionbetween the tongue 489 and the groove 488.

FIGS. 16A-Y show non-limiting examples of a tongue 489 and groove 488connection in which each tongue 489 and groove 488 are oriented in ahorizontal plane. In some aspects, the tongue 489 and groove 488 may beoriented in a vertical plane. For example, as shown in FIGS. 17A-D, anintegration plate 482 may comprise one or more posts 484, with each post484 comprising one or more vertically oriented tongues 489. Eachvertically oriented tongue 489 preferably mates with a correspondingvertically oriented groove 488 in the hole 412. The posts 484 may, forexample, have a star shape (FIGS. 17A and 17B) with the edges of thestars forming both tongues 489 and grooves 488, and the holes 412 mayhave a reciprocal star shape (FIGS. 17C and 17D) with the edges of thestars forming reciprocal grooves 488 and tongues 489.

When the integration plate 482 is pressed together with the implant 401(shown in the drawings as a box only for illustration purposes), thepost 484 is inserted into its corresponding hole 412, and the verticallyoriented tongue 489 is inserted into its corresponding verticallyoriented groove 488. Each post 484, including its vertically orientedtongues 489, preferably has a wider diameter than the corresponding hole412, including the vertically oriented grooves 488, such that a tightfriction fit is established and maintained between the post 484 and thehole 412. Optionally, an adhesive may be used to further strengthen theconnection.

Example Surgical Methods

The following examples of surgical methods are included to more clearlydemonstrate the overall nature of the invention. These examples areexemplary, not restrictive, of the invention.

Certain embodiments of the invention are particularly suited for useduring interbody spinal implant procedures currently known in the art.For example, the disc space may be accessed using a standard mini openretroperitoneal laparotomy approach. The center of the disc space islocated by AP fluoroscopy taking care to make sure the pedicles areequidistant from the spinous process. The disc space is then incised bymaking a window in the annulus for insertion of certain embodiments ofthe spinal implant 1 (a 32 or 36 mm window in the annulus is typicallysuitable for insertion). The process according to the inventionminimizes, if it does not eliminate, the cutting of bone. The endplatesare cleaned of all cartilage with a curette, however, and asize-specific rasp (or broach) may then be used.

Use of a rasp preferably substantially minimizes or eliminates removalof bone, thus substantially minimizing or eliminating impact to thenatural anatomical arch, or concavity, of the vertebral endplate whilepreserving much of the apophyseal rim. Preservation of the anatomicalconcavity is particularly advantageous in maintaining biomechanicalintegrity of the spine. For example, in a healthy spine, the transfer ofcompressive loads from the vertebrae to the spinal disc is achieved viahoop stresses acting upon the natural arch of the endplate. Thedistribution of forces, and resultant hoop stress, along the naturalarch allows the relatively thin shell of subchondral bone to transferlarge amounts of load.

During traditional fusion procedures, the vertebral endplate naturalarch may be significantly removed due to excessive surface preparationfor implant placement and seating. This is especially common where theimplant is to be seated near the center of the vertebral endplate or theimplant is of relatively small medial-lateral width. Breaching thevertebral endplate natural arch disrupts the biomechanical integrity ofthe vertebral endplate such that shear stress, rather than hoop stress,acts upon the endplate surface. This redistribution of stresses mayresult in subsidence of the implant into the vertebral body.

Preferred embodiments of the surgical method minimize endplate boneremoval on the whole, while still allowing for some removal along thevertebral endplate far lateral edges where the subchondral bone isthickest. Still further, certain embodiments of the interbody spinalimplant 1, 101, 101 a, 201, and 301 include smooth, rounded, and highlyradiused posterior portions and lateral sides which may minimizeextraneous bone removal for endplate preparation and reduce localizedstress concentrations. Thus, interbody surgical implant 1, 101, 101 a,201, and 301 and methods of using it are particularly useful inpreserving the natural arch of the vertebral endplate and minimizing thechance of implant subsidence.

Because the endplates are spared during the process of inserting thespinal implant 1, 101, 101 a, 201, and 301, hoop stress of the inferiorand superior endplates is maintained. Spared endplates allow thetransfer of axial stress to the apophasis. Endplate flexion allows thebone graft placed in the interior of the spinal implant 1 to accept andshare stress transmitted from the endplates. In addition, sparedendplates minimize the concern that BMP might erode the cancellous bone.

Interbody spinal implant 1 is durable and can be impacted between theendplates with standard instrumentation. Therefore, certain embodimentsof the invention may be used as the final distractor duringimplantation. In this manner, the disc space may be under-distracted(e.g., distracted to some height less than the height of the interbodyspinal implant 1) to facilitate press-fit implantation. Further, certainembodiments of the current invention having a smooth and roundedposterior portion (and lateral sides) may facilitate easier insertioninto the disc space. Still further, those embodiments having a surfaceroughened topography 80 may lessen the risk of excessive bone removalduring distraction as compared to implants having teeth, ridges, orthreads currently known in the art even in view of a press-fit surgicaldistraction method. Nonetheless, once implanted, the interbody surgicalimplant 1 may provide secure seating and prove difficult to remove.Thus, certain embodiments of the interbody spinal implant 1, 101, 101 a,201, and 301 may maintain a position between the vertebral endplatesdue, at least in part, to resultant annular tension attributable topress-fit surgical implantation and, post-operatively, improvedosteointegration at the top surface 10, 110, 110 a, 210, and 310; thebottom surface 20, 120, 120 a, 220, and 320; or both surfaces.

Surgical implants and methods tension the vertebral annulus viadistraction. These embodiments and methods may also restore spinallordosis, thus improving sagittal and coronal alignment. Implant systemscurrently known in the art require additional instrumentation, such asdistraction plugs, to tension the annulus. These distraction plugsrequire further tertiary instrumentation, however, to maintain thelordotic correction during actual spinal implant insertion. If tertiaryinstrumentation is not used, then some amount of lordotic correction maybe lost upon distraction plug removal. Interbody spinal implant 1,according to certain embodiments of the invention, is particularlyadvantageous in improving spinal lordosis without the need for tertiaryinstrumentation, thus reducing the instrument load upon the surgeon.This reduced instrument load may further decrease the complexity, andrequired steps, of the implantation procedure.

Certain embodiments of the spinal implant 1, 101, 101 a, 201, and 301may also reduce deformities (such as isthmic spondylolythesis) caused bydistraction implant methods. Traditional implant systems requiresecondary or additional instrumentation to maintain the relativeposition of the vertebrae or distract collapsed disc spaces. Incontrast, interbody spinal implant 1, 101, 101 a, 201, and 301 may beused as the final distractor and thus maintain the relative position ofthe vertebrae without the need for secondary instrumentation.

Certain embodiments collectively comprise a family of implants, eachhaving a common design philosophy. These implants and the associatedsurgical technique have been designed to address at least the ten,separate challenges associated with the current generation oftraditional anterior spinal fusion devices listed above in theBackground section of this document.

Embodiments of the invention allow end-plate preparation withcustom-designed rasps. These rasps preferably have a geometry matchedwith the geometry of the implant. The rasps conveniently removecartilage from the endplates and remove minimal bone, only in thepostero-lateral regions of the vertebral end-plates. It has beenreported in the literature that the end-plate is the strongest inpostero-lateral regions.

After desired annulotomy and discectomy, embodiments of the inventionfirst adequately distract the disc space by inserting (throughimpaction) and removing sequentially larger sizes of very smoothdistractors, which have been size matched with the size of the availableimplant 1. Once adequate distraction is achieved, the surgeon preparesthe end-plate with a rasp. There is no secondary instrumentationrequired to keep the disc space distracted while the implant 1, 101, 101a, 201, and 301 is inserted, as the implant 1, 101, 101 a, 201, and 301has sufficient mechanical strength that it is impacted into the discspace. In fact, the height of the implant 1, 101, 101 a, 201, and 301 ispreferably about 1 mm greater than the height of the rasp used forend-plate preparation, to create some additional tension in the annulusby implantation, which creates a stable implant construct in the discspace.

The implant geometry has features which allow it to be implanted via anyone of an anterior, antero-lateral, or lateral approach, providingtremendous intra-operative flexibility of options. The implant 1, 101,101 a, 201, and 301 is designed such that all the impact loads areapplied only to the titanium part of the construct. Thus, the implant 1,101, 101 a, 201, and 301 has adequate strength to allow impact. Thesides of the implant 1, 101, 101 a, 201, and 301 have smooth surfaces toallow for easy implantation and, specifically, to prevent binding of theimplant 1, 101, 101 a, 201, and 301 to soft tissues during implantation.

The invention encompasses a number of different implant 1, 101, 101 a,201, and 301 configurations, including a one-piece, titanium-onlyimplant and a composite implant formed of top and bottom plates(components) made out of titanium. The surfaces exposed to the vertebralbody are dual acid etched to allow for bony in-growth over time, and toprovide resistance against expulsion. The top and bottom titanium platesare assembled together with the implant body that is injection moldedwith PEEK. The net result is a composite implant that has engineeredstiffness for its clinical application. The axial load is borne by thePEEK component of the construct.

It is believed that an intact vertebral end-plate deflects like adiaphragm under axial compressive loads generated due to physiologicactivities. If a spinal fusion implant is inserted in the prepared discspace via a procedure which does not destroy the end-plates, and if theimplant contacts the end-plates only peripherally, the central dome ofthe end-plates can still deflect under physiologic loads. Thisdeflection of the dome can pressurize the bone graft material packedinside the spinal implant, hence allowing it to heal naturally. Theimplant 1, 101, 101 a, 201, and 301 designed according to certainembodiments allows the vertebral end-plate to deflect and allows healingof the bone graft into fusion.

The roughened topography 80, 180, 180 a, 280, and 380 whether directlyon the top/bottom surface of the implant 1, 101, 101 a, 201, and 301 orthe integration plate 82, 182, 182 a, 282, and 382 reacts withcontacting bone to promote biologic activities that facilitate fusion ofbone to the implant 1, 101, 101 a, 201, and 301. The implant 1, 101, 101a, 201, and 301 is configured to resist movement after being seated inthe joint space of the spine. To enhance movement resistance and provideadditional stability under spinal loads in the body, the implant 1, 101,101 a, 201, and 301 may comprise one or more anti-expulsion edges 8,108, 108 a, 208, and 308 that tend to “dig” into the end-plates slightlyand help to resist expulsion (FIGS. 18A-18M). The anti-expulsion edges8, 108, 108 a, 208, and 308 may be present on the top surface 10, 110,110 a, 210, and 310; the bottom surface 20, 120, 120 a, 220, and 320; orboth surfaces of the implant 1, 101, 101 a, 201, and 301.

By way of example, FIG. 18A shows an anti-expulsion edge 8 on the topsurface 10 and bottom surface 20 of the anterior face 40 of the implant1. Each anti-expulsion edge 8 protrudes above the plane of the topsurface 10 and bottom surface 20, with the amount of protrusionincreasing toward the anterior face 40 and the highest protrusion heightP at the anterior-most edge of the top surface 10 or bottom surface 20.As shown in FIG. 18B, the protruding anti-expulsion edge 8 exposes aprotruding surface 9.

An anti-expulsion edge 8, 108, 108 a, 208, and 308 may be orientedtoward the anterior portion 40, 140, 140 a, 240, and 340, or theposterior portion 50, 150, 150 a, 250, and 350, or either of theopposing lateral sides 30, 130, 130 a, 230, and 330. The orientation ofthe anti-expulsion edge 8, 108, 108 a, 208, and 308 may depend on theintended orientation of the implant 1, 101, 101 a, 201, and 301 when ithas been implanted between vertebrae in the patient.

FIGS. 18C-18H show different perspective views of different embodimentsof the implant 101 and 101 a, with the amount of protrusion increasingtoward the posterior face 150 and 150 a and the highest protrusionheight P at the posterior-most edge of the top surface 110 and 110 a orbottom surface 120 and 120 a. The protruding anti-expulsion edge 108 and108 a exposes a protruding surface 109 and 109 a. FIGS. 18I-18K showdifferent perspective views of an embodiment of the implant 301, withthe amount of protrusion increasing toward one of the opposing lateralsides 330 and the highest protrusion height P at the most lateral edgeof the top surface 310 or bottom surface 320. The protrudinganti-expulsion edge 308 exposes a protruding surface 309. FIGS. 18L and18M show different perspective views of an embodiment of the implant201, with the amount of protrusion increasing toward the anteriorportion 240 and the highest protrusion height P at the anterior-mostedge of the top surface 210 or bottom surface 220. The protrudinganti-expulsion edge 208 exposes a protruding surface 209.

In some preferred embodiments, the integration plate 82, 182, 182 a,282, and 382 establishes the anti-expulsion edge 8, 108, 108 a, 208, and308 for either or both of the top surface 10, 110, 110 a, 210, and 310and bottom surface 20, 120, 120 a, 220, and 320 of the implant 1, 101,101 a, 201, and 301. Different integration plates 82, 182, 182 a, 282,and 382 may be used to establish a range of highest protrusion heightsP.

When an integration plate 82 is used, it is preferred that the posteriorportion 51 is substantially flush with the posterior portion edges ofthe implant 1, for example, by having a thickness equivalent to therecess depth D. In other words, it is preferred that the junction of theposterior portion 51 of the integration plate 82 with the implant 1 notprotrude higher than the plane of the top surface 10 or bottom surface20 of the implant 1. FIG. 19A shows a cross-section of the implant 1with an integration plate 82 having a protruding anti-expulsion edge 8,and FIG. 19B shows a close-up of the joint of the integration plate 82and the top surface 10 of the implant 1.

The posterior portion 51 of the integration plate 82 may comprisedifferent edge features. FIGS. 20A-D show non-limiting examples ofpossible configurations of the posterior portion 51 of the integrationplate 82, with FIGS. 20B-D showing an enlarged view of the posteriorportion 51 as encircled in FIG. 20A. For example, the posterior portion51 may have a substantially straight edge as shown in FIG. 20A and FIG.20B, such that the edge of the posterior portion 51 aligns with acorresponding straight edge in the posterior portion 50 of the implant1. In some alternative aspects, the posterior portion 51 may have asubstantially straight edge, and include a beveled edge or chamfer 51Cas shown in FIG. 20C. In some alternative aspects, the posterior portion51 may have a generally blunt nosed profile, including a generallyrounded profile 51D as shown in FIG. 20D.

The implant 1, 101, 101 a, 201, and 301 may comprise a lordotic angle L,e.g., may be wedge-shaped to facilitate sagittal alignment. Thus, forexample, the anterior portion 40, 140, 140 a, 240, and 340 of theimplant 1, 101, 101 a, 201, and 301 may comprise a height that is largerthan the height of the posterior portion 50, 150, 150 a, 250, and 350.The lordotic angle L may be established by the implant 1, 101, 101 a,201, and 301 itself, or may be established by the integration plate 82,182, 182 a, 282, and 382 when combined with the implant 1, 101, 101 a,201, and 301.

The lordotic angle L of the implant 1 preferably closely approximates,or otherwise is substantially the same as, the angle of lordosis of thespine of the patient where the implant 1, 101, 101 a, 201, and 301 willbe implanted. In some aspects, the integration plate 82, 182, 182 a,282, and 382 increases the lordotic angle L by about 3% to about 5%,measured according to the angle of lordosis of a particular patient'sspine. For example, as shown in FIG. 21, the anti-expulsion edge 8protrudes to a height sufficient to increase the overall height H of theanterior portion 40 of the implant 1 such that implant 1 has a lordoticangle L that is about 3% to about 5% greater than the patient's angle oflordosis.

The implant 1, 101, 101 a, 201, and 301 may have a lordotic angle Labout 3%, about 3.3%, about 3.5%, about 3.7%, about 4%, about 4.3%,about 4.5%, about 4.7%, or about 5% greater than the patient's angle oflordosis, though percentages greater than 5% or lesser 3% are possible.The increase of about 3% to about 5% preferably results from thecombination of the protruding height of the integration plate 82, 182,182 a, 282, and 382 on the top portion 10, 110, 110 a, 210, and 310 andbottom portion 20, 120, 120 a, 220, and 320 of the implant 1, 101, 101a, 201, and 301.

The expulsion-resistant edge 8, 108, 108 a, 208, and 308 may comprise ananti-expulsion edge angle E, for example, as shown in FIG. 22 withrespect to the implant 1. The anti-expulsion edge angle E may be fromabout 80 degrees to about 100 degrees. In preferred aspects, theanti-expulsion edge angle E may be measured by taking into account thelordosis angle L of the implant 1, 101, 101 a, 201, and 301. In highlypreferred aspects, the anti-expulsion edge angle E is measured bysubtracting half of the lordotic angle L from 90 degrees. For example,where the lordosis angle L of the implant 1, 101, 101 a, 201, and 301 is12 degrees, the anti-expulsion edge angle E is 84 degrees (90−(12×0.5)).The anti-expulsion edge angle E may be about 80 degrees, about 81degrees, about 82 degrees, about 83 degrees, about 84 degrees, about 85degrees, about 86 degrees, about 86.5 degrees, about 87 degrees, about88 degrees, or about 89 degrees.

The top and bottom surfaces of the implant may be made out of titaniumand are dual acid etched. The dual acid etching process creates a highlyroughened texture on these surfaces, which generates tremendousresistance to expulsion. The width of these dual acid etched surfaces isvery broad and creates a large area of contact with the vertebralend-plates, further increasing the resistance to expulsion.

The implant 1 according to certain embodiments of the invention has alarge foot-print, and offers several sizes. Because there is nosecondary instrument required to maintain distraction duringimplantation, all the medial-lateral (ML) exposure is available asimplantable ML width of the implant. This feature allows the implant tocontact the vertebral end-plates at the peripheral apophyseal rim, wherethe end-plates are the strongest and least likely to subside.

Further, there are no teeth on the top and bottom surfaces (teeth cancreate stress risers in the end-plate, encouraging subsidence). Exceptfor certain faces, all the implant surfaces have heavily rounded edges,creating a low stress contact with the end-plates. The wide rim of thetop and bottom surfaces, in contact with the end-plates, creates alow-stress contact due to the large surface area Finally, the implantconstruct has an engineered stiffness to minimize the stiffness mismatchwith the vertebral body which it contacts.

The implant 1 according to certain embodiments of the invention has alarge foot-print. In addition, titanium provides high strength for asmall volume. In combination, the large foot-print along with theengineered use of titanium allows for a large volume of bone graft to beplaced inside the implant.

It is believed that an intact vertebral end-plate deflects like adiaphragm under axial compressive loads generated due to physiologicactivities. If a spinal fusion implant is inserted in the prepared discspace via a procedure which does not destroy the end-plate, and if theimplant contacts the end-plates only peripherally, the central dome ofthe end-plates can still deflect under physiologic loads. Thisdeflection of the dome can pressurize the bone graft material packedinside the spinal implant, hence allowing it to heal naturally. Theimplant 1 according to certain embodiments of the invention allows thevertebral end-plate to deflect and facilitates healing of the bone graftinto fusion.

The top and bottom surfaces of the implant 1 according to certainembodiments of the invention are made of titanium and are dual acidetched. The dual acid etched surface treatment of titanium allowsin-growth of bone to the surfaces. Hence, the implant 1 is designed toincorporate with the vertebral bone over time. It may be that thein-growth happens sooner than fusion. If so, there may be an opportunityfor the patients treated with the implant 1 to return to normal activitylevels sooner than currently recommended by standards of care.

Even the titanium-only embodiment of the invention has been designedwith large windows to allow for radiographic evaluation of fusion, boththrough AP and lateral X-rays. A composite implant minimizes the volumeof titanium, and localizes it to the top and bottom surfaces. The restof the implant is made of PEEK which is radiolucent and allows for freeradiographic visualization.

Although illustrated and described above with reference to certainspecific embodiments and examples, the invention is nevertheless notintended to be limited to the details shown. Rather, variousmodifications may be made in the details within the scope and range ofequivalents of the claims and without departing from the spirit of theinvention. It is expressly intended, for example, that all rangesbroadly recited in this document include within their scope all narrowerranges which fall within the broader ranges. In addition, features ofone embodiment may be incorporated into another embodiment.

1. An interbody spinal implant, comprising: a body having a top surface,a bottom surface, opposing lateral sides, opposing anterior andposterior portions, a substantially hollow center, and a single verticalaperture extending from the top surface to the bottom surface, having asize and shape for maximizing the surface area of the top surface andthe bottom surface available proximate the anterior and posteriorportions, defining a transverse rim with a varying width or thickness,and having a maximum width at its center, wherein at least a portion ofthe top surface of the body, and optionally the bottom surface of thebody, is recessed and comprises a plurality of holes; and at least oneintegration plate having a top surface, a bottom surface, opposinglateral sides, opposing anterior and posterior portions, and a singlevertical aperture extending from the top surface to the bottom surfaceand aligning with the single vertical aperture of the body, defining atransverse rim with a varying width or thickness, and having a maximumwidth at its center, wherein the top surface of the integration platecomprises a roughened surface topography adapted to grip bone andinhibit migration of the implant, and wherein the bottom surface of theintegration plate comprises a plurality of posts positioned to alignwith the plurality of holes and affix the integration plate to the body.2. The interbody spinal implant of claim 1, wherein the body and theintegration plate are each comprised of a metal.
 3. The interbody spinalimplant of claim 1, wherein the body is comprised of a non-metal polymerand the integration plate is comprised of a metal.
 4. The interbodyspinal implant of claim 3, wherein the non-metal polymer is selectedfrom the group consisting of polyetherether-ketone, hedrocel, andultra-high molecular weight polyethylene.
 5. The interbody spinalimplant of claim 1, wherein the body is comprised of a composite of ametal and a non-metal polymer selected from the group consisting ofpolyetherether-ketone, hedrocel, and ultra-high molecular weightpolyethylene.
 6. The interbody spinal implant of claim 1, wherein thebody and the integration plate are generally oval-shaped in transversecross-section.
 7. The interbody spinal implant of claim 1, wherein thebody and the integration plate are generally rectangular-shaped intransverse cross-section.
 8. The interbody spinal implant of claim 1,wherein the body and the integration plate are generally curved-shapedin transverse cross-section.
 9. The interbody spinal implant of claim 1,wherein the anterior portion of the body or the posterior portion of thebody comprises an opening for achieving one or more of the followingfunctions: being adapted to engage a delivery device, facilitatingdelivery of bone graft material to the substantially hollow center,enhancing visibility of the implant, and providing access to bone graftmaterial.
 10. The interbody spinal implant of claim 1, furthercomprising bone graft material disposed in the substantially hollowcenter of the body and adapted to facilitate the formation of a solidfusion column within the spine.
 11. The interbody spinal implant ofclaim 10, wherein the bone graft material is cancellous autograft bone,allograft bone, demineralized bone matrix (DBM), porous synthetic bonegraft substitute, bone morphogenic protein (BMP), or a combinationthereof.
 12. The interbody spinal implant of claim 10, furthercomprising a wall closing at least one of the opposing anterior andposterior portions of the body to contain the bone graft material. 13.The interbody spinal implant of claim 1, wherein the recessed portion ofthe top surface, and optionally wherein the recessed portion of thebottom surface, are recessed to a depth corresponding to the thicknessof the integration plate.
 14. The interbody spinal implant of claim 1further comprising a lordotic angle adapted to facilitate alignment ofthe spine.
 15. The interbody spinal implant of claim 1, wherein theinterbody spinal implant is adapted to be inserted into a prepared discspace via a procedure which does not destroy the vertebral end-plates orto contact the vertebral end-plates only peripherally, allowing theintact vertebral end-plates to deflect like a diaphragm under axialcompressive loads generated due to physiologic activities and pressurizethe bone graft material disposed inside the spinal implant.
 16. Theinterbody spinal implant of claim 1, wherein at least one of theanterior and posterior portions of the integration plate comprise ananti-expulsion edge to resist pullout of the implant from the spine of apatient into which the implant has been implanted.
 17. The spinalimplant of claim 2, wherein the metal comprises titanium.
 18. The spinalimplant of claim 1, wherein the anterior portion of the integrationplate has a greater thickness than the thickness of the posteriorportion of the integration plate.
 19. The spinal implant of claim 1,wherein the posterior portion of the integration plate has a greaterthickness than the thickness of the anterior portion of the integrationplate.
 20. The spinal implant of claim 1, wherein one of the opposinglateral sides of the integration plate has a greater thickness than theother of the opposing lateral sides of the integration plate.